In the forests of Tsinjoarivo in eastern central Madagascar, an unusual population of what appears to be P. diadema has been discovered. The animals are variably coloured, including all black individuals (several of which are known to have been born to parents with typical pelage), but preliminary genetic studies indicate that this population requires further study before subspecific status can be established (Mayor et al. 2004).

A population reduction of ≥80% is suspected to be met in the future (over a three generation time period of 45 years). This is based on a continuing decline in area, extent and quality of habitat due to slash-and-burn agricultural practices and timber extraction as principal threats, planting of sugar cane fields and destructive utilisation of sifaka food trees in some areas, in addition to exploitation through unsustainable hunting pressure. Based on these premises, the species is listed as Critically Endangered.

This species is found in eastern and northeastern Madagascar. Although the precise limits of its range are unknown this species is thought to be one of the most widely-distributed of the sifakas, occurring throughout the island’s eastern rainforests from the Mangoro and Onive rivers north to the Mananara River. Historically, its range extended farther north to just south of the Antainambalana River, but it has not been found in recent years during fairly extensive studies of that region (Mittermeier et al. 2013).

This species is rare. It occurs only at very low densities wherever it is found: at Tsinjoarivo densities of 7 individuals/km2 were recorded in less-disturbed, continuous forest, with higher local densities in some smaller fragments (Irwin 2008a). Population figures are in decline due to habitat destruction and hunting.

It is found in the eastern rainforests, and persists in some smaller forest fragments (down to ~30 ha). The diet consists mainly of ripe fruits, seeds, flowers, and young leaves, their respective proportions varying according to seasonal abundance (Irwin 2008b). Females are sexually receptive for very few days (perhaps only one day) out of the year, sometime between November and January. A single young is born between May and July, after a gestation of 179 days. Individuals may live up to 20 years in the wild. This species is diurnal and arboreal. In one study, these animals spent 49·4% of their time resting, 37·8% feeding, 2·4% in social behaviour, 5·1% moving, and the remainder in other activities. This species has only twice been studied for a significant period of time (by Powzyk at Mantadia and Irwin at Tsinjoarivo). It lives in female-dominated, multi-male/multi -female groups of 2 to 8 individuals, consisting of 1–3 adult females and 1 or 2 adult males, and multiple females may breed within the same group. Exclusive territories of 20–80 ha are maintained by means of scent-marking, although there is little aggression over boundaries. Compared to the sympatric, similar -sized Indri indri, P. diadema spends more time actively patrolling and defending its territories. The mean daily path length of 987– 1629 m for P. diadema can be compared to 774 m for I. indri (Powzyk 1997). Predation by fosa (Cryptoprocta ferox) may be an important threat to this species, especially in fragmented or degraded areas where other prey species may be reduced (Irwin et al. 2009). Males emigrate at age five, often to a neighbouring group; females may either emigrate or remain in their natal group (Mittermeier et al. 2010 and references therein)

Continued destruction of rain forest habitat in eastern Madagascar due to slash-and-burn agricultural practices and timber extraction is the principal threat to this sifaka’s survival, although hunting for food also can have a very serious impact on remaining populations, even within existing protected areas (Mittermeier et al. 2010). Furthermore, illegal rum production, necessitating the planting of sugar cane fields and destructive utilization of sifaka food trees, is a threat to populations in Tsinjoarivo (Irwin and Ravelomanantsoa 2004).

This species is listed on Appendix I of CITES. This species occurs in three national parks (Mananara-Nord, Mantadia, and Zahamena), two strict nature reserves (Betampona and Zahamena), and three special reserves (Ambatovaky, Mangerivola, and Marotandrano) (Mittermeier et al. 2010). Additional populations have been identified in the Andriantantely Classified Forest, Tsinjoarivo Classified Forest, the Marokitay Forest Reserve, and in the unprotected forests of Anosibe an’ala, Anjozorobe, Didy, Iofa, Maromiza and Sandranantitra (Mittermeier et al. 2010). The Tsinjoarivo Classified Forest has already been recommended as a new protected area. As of 2012 this species was not represented in captivity.

In-Place Research, Monitoring and PlanningIn-Place Land/Water Protection and Management Conservation sites identified:Yes, over entire range Occur in at least one PA:YesIn-Place Species ManagementIn-Place Education Included in international legislation:Yes Subject to any international management/trade controls:Yes